Thermal lens technique: a new method of absorption spectroscopy

Area of Science:

• Analytical Chemistry
• Spectroscopy

Background:

• Measuring trace amounts of colorless organic compounds presents analytical challenges.
• Conventional spectroscopic methods often require long optical paths for sensitive measurements.

Purpose of the Study:

• To apply the thermal lens technique for quantifying "colorless" organic compounds.
• To identify and characterize combination overtones of C-H stretching vibrations.
• To determine the sensitivity and accuracy of the thermal lens technique for spectroscopic analysis.

Main Methods:

• Utilized both single beam and dual beam (with synchronous detection) thermal lens spectroscopy.
• Investigated spectral range from 15,700 to 17,400 cm-1.
• Measured extinction coefficients and So to T1 absorption spectra.

Main Results:

• Successfully identified combination overtones of C-H stretching vibrations in benzene.
• Accurately determined extinction coefficients as low as 1 x 10^-6 L mol^-1 cm^-1.
• Measured the So to T1 absorption of anthracene, showing favorable comparison with conventional techniques.

Conclusions:

• The thermal lens technique is a sensitive and accurate method for analyzing "colorless" organic compounds.
• The technique effectively characterizes vibrational overtones and electronic transitions.
• Demonstrated the utility of thermal lens spectroscopy for quantitative and qualitative analysis in specific spectral regions.